Pentax lens mount question

Steve Mack · May 4, 2008

Hello, everybody:

I want to thanak all of those who replied to my question about getting my Pentax K1000 CLA'd. Now I have a question regarding the lens mount.

On KEH's website, I was looking for a 50 mm lens for my Pentax K1000. The lenses on KEH's site are listed as follows, for example: 50 F1.7 SMC A and 50 F1.7 SMC M. NO mention of the K-mount. What's up? Will these lenses fit the K-mount? I am not familiar with the K-mount and which lenses will fit, and I could used some help. Obviously I am missing something,and I'd hate to order a lens and have to exchange it because I didn't get the model number right in the first place.

Thanks to all who reply.

With best regards,

Steve Mack

MartinB · May 4, 2008

The short answer is that both are K mount and will work on the K 1000. The A has additional contacts that more advanced bodies use so if you plan on getting another body it might be a consideration.

A good resource for K mount is Bojidar Dimitrov's website.

Martin

Anscojohn · May 4, 2008

Steve,
You should be able to locate used K mount lenses without too much trouble. Although KEH is reputable, you might do better shopping around at flea markets and places like that.

phenix · May 4, 2008

Indeed, the no. 1 reference in Pentax bodies and lenses is Bojidar Dimitrov - you'll find there all about Pentax.

Besides that, if you are looking for a 50mm Pentax lens, forget the 50mm f:2 - it has only 5 elements (a shame). On the other hand, the f:1.7 and f:1.4, are all beautiful lenses. And you also can check with other manufacturers like Ricoh who also sold under the label of Sears who made very contrasty lenses (excellent for slides), Chinon (very precise, but somehow technical outputs), Cosina and Vivitar who's 50/1.7 is a beauty (precise, still very gentle outputs). All these made 50mm f:2 and f:1.7 with 6 elements, and f:1.4 with 7elements. For aditional information about K-mount lenses and bodies other than Pentax, the reference is Butkus: http://www.butkus.org/chinon/index.html

Stevopedia · May 5, 2008

All of the pictures I've ever taken with my smc P-M 50/2 look fine to me...

Please forgive the ignorance of my question, but what does the number of elements in a lens do for the quality of the photograph? The only affect I can think of a larger number of elements having is an increase in lens flare...

At any rate, most (if not all) of the Pentax primes are wonderful, and they won't disappoint. Also, if you can find one, an adapter exists that allows you to use M42 (i.e. Takumar) lenses on a K-mount camera. The Takumars (which are the lenses that Pentax made for its Spotmatic line) are just as nice as the K-mount Pentax lenses, if not nicer.

Anscojohn · May 5, 2008

[ Also, if you can find one, an adapter exists that allows you to use M42 (i.e. Takumar) lenses on a K-mount camera.
*****
Such an adapter opens up a universe of opportunities, since any of the Pentax-Practika screw mount lenses may be used--not just Takumars.

srs5694 · May 5, 2008

Adapters to mount M42 on K-mount are pretty common. I believe B&H sells them, among others. The geometries involved mean that the adapter is just a hunk of metal with a thread inside and a K-mount ring on the outside; no optics are required. One caveat, though: "Automatic" M42 lenses, with the pin that stops down the aperture, don't work well with most adapters, since the adapters don't work that pin. I vaguely recall hearing of an adapter that will stop down the pin, but I don't recall the details, and I could be misremembering.

Elox · May 5, 2008

srs5694 said:
Adapters to mount M42 on K-mount are pretty common. I believe B&H sells them, among others. The geometries involved mean that the adapter is just a hunk of metal with a thread inside and a K-mount ring on the outside....

Be careful with any that you find on ebay or some camera shows. Some do not mount flush like the Pentax version and will not allow infinity focus. The Pentax made versions are best but they are getting hard to find. And no, I'm not selling either of mine......

phenix · May 6, 2008

While beautiful, screw mount lenses (M42) will limit you when focussing and metering: M42 do not meter with the aperture wide open like K-mount lenses. So, you'll have to make the focus with the aperture wide open, than close it manually in order to adjust it with the shooter time. I really don't see an advantage in M42, as they are neither better, nor worser, than K-mount lenses. Maybe cheaper, but with today's drop in prices does this really matter?

To Stevopedia: What do the numbers of elements in a lens count? Well, in 35mm it does a lot. In LF it does far less. Let's put it in another way: what enlarging lenses do you prefer - 4el/tessars or 6el? I also found a 5el enlarging lens, a russian one (Vega), but at least this is a "hot" lens (with 1el of radioactive Lanthanium making it equivalent to 6el lenses) and it is my beloved for portraits. Back to 35mm: if you want to avoid flare, the best is to look for a multicoated lens. Even 4el/Tessars or 3el are giving flare if simple coated. By reducing the number of elements in a lens you do not avoid the flare, but only the image quality. I had the Pentax 50/2, and had to pray for somebody to buy it for 20$ Canadians (12-13$ US at that time). And by that time lenses prices were still high - it was the time when there were no digital cameras over 1MP, and nobody believed in digital yet.

BTW, many M42 lenses are simple or double coated. Some K-mount are too, but far less. Pentax's SMC stays for Super Multi-Coated, and it means 5 or 7 coating layers (7 I think), and this is the best coating system ever done (I mean even today it isn't overpassed by any other manufacturer). But forget about the 50/2 even if SMC...

srs5694 · May 6, 2008

phenix said:
I also found a 5el enlarging lens, a russian one (Vega), but at least this is a "hot" lens (with 1el of radioactive Lanthanium making it equivalent to 6el lenses) and it is my beloved for portraits.

I've also got a Vega 11U enlarger lens. I know of one other FSU/Russian lens that's said to have some lanthanum (the Industar 61L/D, which shipped with later FEDs), but I wasn't aware the Vega 11U (if that's the model you mean) also used lanthanum. I'm curious: Why do you like that lens for portraits?

David H. Bebbington · May 6, 2008

Stevopedia said:
...
Please forgive the ignorance of my question, but what does the number of elements in a lens do for the quality of the photograph? The only affect I can think of a larger number of elements having is an increase in lens flare...

...

A larger number of elements in a lens FUNDAMENTALLY gives a lens designer more possibilities of correcting lens aberrations (which degrade image quality). However, since flare is a measure of how much light gets scattered as it passes through a piece of glass, instead of staying focused as you want it to, more elements also FUNDAMENTALLY mean more flare. Before lens coating came in in the 1940s, this meant that a 4-element Tessar-type lens would always have more contrast than a 6-element Gauss-type (AKA plasmat) lens. Press photographers using Leica, for example, would have both a 4-element Elmar and a 7-element Xenon and use the Xenon only when they needed the extra speed, since the flare was otherwise excessive. The same principle applies to the single-coated lenses of the 40s and 50s - a Schneider Xenar has more contrast than a Xenon (but not as flat a field).

With super-multi-coating, which came in in the 60s, this difference is much less pronounced, and in fact the difference in contrast between 4- and 6-element prime lenses and even zoom lenses is far smaller, for practical purposes negligible, except that prime lenses almost always have better flatness and zooms, particularly older ones, may have a spot in the zoom range where flare suddenly explodes.

phenix · May 7, 2008

srs5694 said:
I've also got a Vega 11U enlarger lens. I know of one other FSU/Russian lens that's said to have some lanthanum (the Industar 61L/D, which shipped with later FEDs), but I wasn't aware the Vega 11U (if that's the model you mean) also used lanthanum. I'm curious: Why do you like that lens for portraits?

Yes, it is the Vega 11U. The mount is orfull, but the optics are beauteful. Why for portraits? Because it seams a bit soft at the edges, while crisp but also "gentle" in the middle. I use it in f/5.6, but maybe I should try it in f/8 too...

Industars also have a lanthanium element. I don't know that of Feds, but the M42 for Zenits is a Tessar type with the back concave element with lantanium. What does this radioactive element do? It makes a 4el lens perform like a 6el one.

But the radioactivity is very low, dangerous maybe if you sleep with the lens on your chest more than 50 years. BTW, Leica also made some radioactive lenses earlier, but they used radium in their glass. US aerial lenses also have radium in their huge back element (being huge maybe is it more dangerous? - I don't know). The radioactive substance plaied the same role today's low distorsion materials do, but somehow (if not much) better.

That's why I love "hot" lenses!

Stevopedia · May 7, 2008

B. Baer said:
A larger number of elements in a lens FUNDAMENTALLY gives a lens designer more possibilities of correcting lens aberrations (which degrade image quality). However, since flare is a measure of how much light gets scattered as it passes through a piece of glass, instead of staying focused as you want it to, more elements also FUNDAMENTALLY mean more flare. Before lens coating came in in the 1940s, this meant that a 4-element Tessar-type lens would always have more contrast than a 6-element Gauss-type (AKA plasmat) lens. Press photographers using Leica, for example, would have both a 4-element Elmar and a 7-element Xenon and use the Xenon only when they needed the extra speed, since the flare was otherwise excessive. The same principle applies to the single-coated lenses of the 40s and 50s - a Schneider Xenar has more contrast than a Xenon (but not as flat a field).

With super-multi-coating, which came in in the 60s, this difference is much less pronounced, and in fact the difference in contrast between 4- and 6-element prime lenses and even zoom lenses is far smaller, for practical purposes negligible, except that prime lenses almost always have better flatness and zooms, particularly older ones, may have a spot in the zoom range where flare suddenly explodes.

Thank you very much for that explanation, B. Baer, I found that to be very informative.

Also, phenix, FWIW, there was at lease one Takumar that had a radioactive element--the 50/1.4 Super Takumar. Some examples of that lens have thorium glass. There could be other radioactive Takumars, though.

phenix · May 7, 2008

I remember Stevopedia, you are right about the Takumar 50/1.4! This was the lens Asahi anounced to have equaled the resolution of a Leica 50/1.4, and tests did prove it (Asahi in f/8, and Leica in f/4 or 5.6). It was an M42 mount, as Pentax didn't introduce the K-mount yet. I think that the later K-mount Takumar, and the next generation of SMC-M 50/1.4 were still the same "hot" lens, plus the super multi-coating, but I'm not at 100% sure. Meanwhile, the SMC-A 50/1.4 was, for sure, not a "hot" lens anymore.

ricksplace · May 8, 2008

I have shot Pentax all my life. The 50/2 is an excellent lens, far underpriced for its capabilities. At f8 there is no difference from the 50/1.4. I have three 50/2, and all compare favourably to the 50/1.4. If I need to shoot at f4 or larger, I use the 50/1.4. The 1.4 is better at the wide aperatures.

As for the number of elements, I have a Schneider Kruesnach Radionar (three element) 80/2.9 on a folder that is absolutely stunning when used in its oprimal f-stop range of f8-f16. I also have a 105/3.5 Rodenstock Trinar on a folder that is not sharp in the corners (6X9) except at f22. Ya just have to try 'em...

phenix · May 9, 2008

ricksplace said:
As for the number of elements, I have a Schneider Kruesnach Radionar (three element) 80/2.9 on a folder that is absolutely stunning when used in its oprimal f-stop range of f8-f16. I also have a 105/3.5 Rodenstock Trinar on a folder that is not sharp in the corners (6X9) except at f22. Ya just have to try 'em...

The biger the film format you shoot, the lower are the requirements a lens has to meet.

mawz · May 10, 2008

ricksplace said:
I have shot Pentax all my life. The 50/2 is an excellent lens, far underpriced for its capabilities. At f8 there is no difference from the 50/1.4. I have three 50/2, and all compare favourably to the 50/1.4. If I need to shoot at f4 or larger, I use the 50/1.4. The 1.4 is better at the wide aperatures.

As for the number of elements, I have a Schneider Kruesnach Radionar (three element) 80/2.9 on a folder that is absolutely stunning when used in its oprimal f-stop range of f8-f16. I also have a 105/3.5 Rodenstock Trinar on a folder that is not sharp in the corners (6X9) except at f22. Ya just have to try 'em...

All of the Pentax normals are quite good, the 55/1.8's are a classic design. The 50mm f1.7 is ridiculously sharp (the sharpest of the non-macro 50's), while the 1.4 and 2.0 do better with people and the 1.2 is one of the best 70's-era f1.2 normals. Needless to say the 50 macros are excellent and the 40/2.8 is a tiny wee gem.

The downside to the 50mm f2 is wide-open performance and distortion, but it is very underrated for its performance and a much better lens than many think.

Pentax lens mount question

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